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I would suggest getting a 1967 Service Manual, it has the most complete assembly procedures for the 66-69 OHC-6 engines. I have a slightly beat up spare if you are interested, you can have it for the cost of shipping it to you.
Do not use the 1970 OHV-6 chevy engine spec's for the cam cover. The Torque procedure on a OHC-6 cam cover is very specific, and has to be done in a similar fashion as a head is torqued.
15 ft lbs is the correct torque as melsg5 previously stated.